Прогнозна оцінка ефективності підвищення втомного опору елементів зварних конструкцій термообробкою

Abstract

An analysis of influence on the magnitude of the limiting residual stresses of the cycle of welded joints is performed. An equation for determining the maximum boundary stresses of a cycle subjected to the treatment of a welded joint is obtained. The methodology for calculating the effectiveness of the complete elimination of residual stresses by heat treatment is applicable not only for the case when the output residual stresses in the welded joint reach the value of the material yield strength, but also for the case when these stresses do not exceed the value but above the limit value of the initial residual stresses, in which the maximum stresses in the zones of the weld hubs during cyclic loading reaches the value of the material yield strength.Dependences were obtained for determining the boundary stresses for local heat treatment of metal structures by locally lumped heat fluxes. It has been established that reducing the output level of residual weld stresses increases the boundary of endurance of joints joints. On the basis of the developed method of estimating the impact of residual weld stresses and their redistribution as a result of local heat treatment, the dependence of the limiting value of residual stresses on the coefficient of asymmetry of the external load cycle was investigated.The analysis of the obtained correlations and experimental data indicates that the local heat treatment leads to a significant increase in the boundary stresses and cyclic durability of the welded joints. The effectiveness of such a type of strengthening of the elements of welded structures depends on the mechanical characteristics of materials, parameters of external load, type of connections, etc. The greatest influence of local heat treatment is on the resistance of fatigue welded joints of constructions in conditions of an alternating load cycle.